If your BlackBerry KEYone is stuck in the (often showing a purple LED or the BlackBerry logo and then looping back to the menu), it usually indicates a corruption in the operating system or a hardware fault with the battery or buttons.

If the above method doesn't work for you, you can try using the BlackBerry Software to repack your device. You'll need to:

The BlackBerry KEYone is a legend—the last gasp of a physical keyboard in a glass slab world. Its bootloader is finicky, its Qualcomm chipset is aging, and its memory partitions are fragile. But thanks to the community’s discovery of the proprietary command, a “stuck in bootloader menu” scenario is no longer a death sentence.

BlackBerry devices are notoriously picky about USB cables. Use the original USB-C cable and a USB 2.0 port if possible.